1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device and a transmission and reception system.
2. Description of the Related Art
In recent years, according to the microminiaturization of devices, one chip including both analog and digital circuits is mainly used and higher integration of IC is advanced. At present, besides portable terminals, a large number of small applications such as game controllers employing radio systems emerge on the market. It is important to reduce power consumption to prevent a waste of batteries as much as possible. A micro-process is applied by product development to realize the lower power consumption and the high integration. Therefore, a reduction in voltage is advanced in high-frequency analog circuits used in the radio systems. In particular, in power amplifiers and the like required to have a liner gain characteristic, a fall in an amplitude margin due to lowering of power supply voltage is an extremely serious problem.
As a technique of obtaining a linear input and output characteristic, a technique of applying pre-distortion to a signal before being input into an amplifier to linearize a total gain characteristic is often used because the technique can be realized by a simple configuration. Above all, a linearizer including a diode is popular. It is possible to adjust a gain characteristic (an AM-AM characteristic) and a phase characteristic (an AM-PM characteristic) of the diode by changing a bias voltage applied to the diode.
Japanese Patent Application Laid-Open No. 2002-9555 discloses that, in a pre-distorter connected to an input side of an amplification element to apply pre-distortion, opposite bias voltages are respectively applied to two diodes having opposite polarities and connected in parallel to each other. Terminal voltages of the two diodes is controlled by freely controlling the opposite bias voltages applied to the two diodes. A position of a distortion start point of the pre-distorter can be adjusted. Consequently, according to Japanese Patent Application Laid-Open No. 2002-9555, only values of the opposite bias voltages are enough for parameters that should be controlled in adjusting a distortion characteristic of the pre-distorter. Therefore, it is possible to simplify adjustment of the distortion characteristic.
In the technique disclose in Japanese Patent Application Laid-Open No. 2002-9555, the opposite bias voltages applied to the two diodes can be freely controlled. For this reason, the technique requires two bias voltage sources that generate continuously-variable two opposite bias voltages having opposite signs. Moreover, to apply bias voltages having different signs to terminals on the earth side of the two diodes, direct current of the two diodes have to be interrupted. For this reason, the technique also requires large capacitance between the two diodes and the earth, respectively. Therefore, in the technique, an area of a circuit used for the adjustment of the distortion characteristic of the pre-distorter increases.